1. Field of the Invention
The present invention relates to a rotary pulsating sprinkler and more particularly to a system for accurately adjusting the force applied to the impact arm by the impact arm spring.
2. Prior Art
Rotary sprinklers in common use today incorporate a rotatable body carrying a laterally directed nozzle for distributing water or other fluids to a desired area. The main body and nozzle are rotated by an impact arm also rotatable with the body which is actuated by the reaction of a stream of water upon the arm. The impact arm is designed with a deflector at its end which intercepts a stream of water from either a primary or secondary nozzle causing the arm to be deflected against a spring which returns the arm for rotational impact with the body thereby rotating the body in successive increments.
Where the impact arm is overdeflected by the stream of water, the sprinkler may not rotate properly or may operate in a direction reverse from the intended direction. Moreover, where the spring prevents sufficient deflection of the impact arm, the rotary sprinkler will fail to operate properly. The biasing force applied by the spring to the arm can also control the speed at which the rotary sprinkler rotates in its operation. Thus, it has become advantageous to provide the capability for adjusting the biasing force applied by the spring to the impact arm.
Normally, a helical spring surrounding the shaft on which the impact arm is journaled controls the biasing force on the arm. Adjustment to the spring is made by coiling and uncoiling the spring to vary the load transmitted to the arm. In some prior art systems, the helical spring is coiled by simply shortening the spring. This is accomplished by drawing one end through its point of attachment to the arm and removing the excess wire after the adjustment. Naturally, such an adjustment becomes irreversible by the mere fact that the excess spring is removed from the spring coil. Moreover, the adjustment can only be made with the sprinkler in the off position.
Other prior art systems have included the attachment of one end of the spring to a cap which is journaled on the shaft about which the impact arm rotates. The cap mates with the shaft through indentions which permit the rotation of the cap relative to the shaft thereby permitting the coiling or uncoiling of the impact arm spring and the resulting adjustment. These systems fail to permit accurate adjustments and, because of the necessity of deforming the mating indention structure in order to adjust the system, result in failure of the system due to the wear resulting from successive adjustments.
To overcome the limitations found in these systems, more positive means for locking the cap member to the shaft of the sprinkler after adjustment have been introduced and include the direct attachment of the cap to the shaft by means of a cotter key which is positioned through apertures in the shaft and corresponding notches in the cap. There systems substantially increase the difficulty and limit the accuracy of the adjustment. Moreover, the adjustment of these systems is difficult if not impossible during the operation of the sprinkler.
The sprinkler head adjustment disclosed in U.S. Pat. No. 3,009,650, Alvarez, discloses still another method of controlling the force applied by the impact arm spring on an impulse sprinkler. This system requires both the disengagement of the head screw and the subsequent rotation of a mounting member therebelow to which the impulse arm spring is attached. Therefore, in this arrangement the adjustment of the impact arm sprinkler cannot be accomplished from above the sprinkler head which is of critical importance where the sprinkler and adjustment structure is obscured by a top cover supported from the sprinkler structure.
Therefore, a need has arisen for a system which provides quick and accurate adjustment of the impact arm spring in a rotary sprinkler while permitting adjustment of the spring during the operation of the sprinkler.